The New Zealand Principals Federation is saying the Education Minister has backed down over a progress and consistency tool for teachers saying it will not be compulsory.

The New Zealand Principals Federation received a letter in May saying the Education Ministry's new $5.2 online progress and consistency tool (PaCT) would be mandatory by 2015.

The PaCT tool gives teachers checks and balances to ask themselves where their student are in terms of meeting yearly educational targets.

New Zealand Principals Federation president Philip Harding said there was little assurance the tool would not be used to other purposes like assessing teachers performance and that it could form a national test.

The federation will continue to boycott the trial and development of the PaCT tool, despite Education Minister Hekia Parata saying it would not be compulsory.

Ms Parata is urging schools to try the tool saying it could be world leading and streamline reporting for teachers and principals.

"It had been my expectation that the tool would be widely available in 2015 and when I realised principals were concerned that this meant it would be an imposition and it would get in the way of them working with the tool, then I wanted to remove that concern.

"There is no other agenda than to deal with the two issues that teachers have consistently raised which is how do you capture progress and how do you get consistent overall teacher judgements,'' Ms Parata said.

She admitted principals were concerned about the tool and its purpose.

"I want to alleviate their concern by confirming it's not my intention to make this compulsory in 2015, but I do expect that it will be universally available.

"I think the tool will mandate itself, that as teachers use it more and have conversations with each other they will want to have it available.

"We know that we are always looking to get better and that's my expectation in terms of getting richer data.

"What the PaCT tool does is help facilitate that.

"Working in a data-rich environment helps the teacher know what the next thing they should do is, helps parents know how they can help with their child's learning, helps the child themselves know.''

Professor of Education at the University of Waikato Martin Thrupp said PACT will only deal with the symptoms on inconsistency in National Standards assessment.

"By failing to recognise the underlying causes of variation, it is likely to allow the Government to ignore the impact of contextual inequalities between schools, for instance, the effects of diverse and unequal intakes and communities, school locations, staffing and other resources.''

He said the tool was intended as a form of moderation and would "be an expensive failure''.